Semiconductor isolation process to minimize weak oxide problems

A process for forming an isolation region while substantially eliminating weak oxide effects, comprising the steps of:

• obtaining a semiconductor substrate patterned with a plurality of mesas with sidewalls, with semiconductor substrate exposed in areas between said mesas, each of said mesas comprising at least a first insulator layer and a second different insulator layer thereover;
• forming a trench between said mesas into said exposed semiconductor substrate;
• removing a lateral portion of said first insulator layer exposed at said sidewalls of said mesas to thereby undercut said second insulator layer at its sidewall edges to thereby expose a further portion of said semiconductor substrate;
• implanting a first material into only said exposed further portion of said semiconductor substrate exposed below said undercut edges of said second insulator material where said lateral portion of said first insulator layer was removed to form an implanted silicon region of said silicon substrate corresponding to top corners of said trench;
• forming an oxide layer on exposed areas of said semiconductor substrate and on said implanted silicon region of said semiconductor substrate;
• removing said first and second insulator layers;
• and
• thermally growing a tunnel oxide layer only onto top surfaces of said each of said mesas,
• wherein said oxide layer formed on said implanted silicon region forms a buffer region to limit electron tunneling between said tunnel oxide layer and said implanted silicon region of said semiconductor substrate.